Redox-responsive nanoparticles from the single disulfide bond-bridged block copolymer as drug carriers for overcoming multidrug resistance in cancer cells

Chemical encoding of amphiphilic copolymers for a dual controlled release from their assemblies

Amphiphilic random copolymers are designed to bear a corrosion inhibitor as cleavable side group, which can be released upon activation by chemical reduction.

Biocompatible and bioreducible micelles fabricated from novel α-amino acid-based poly(disulfide urethane)s: design, synthesis and triggered doxorubicin release

Novel α-amino acid-based poly(disulfide urethane)s have been developed for the construction of smart triblock copolymer micelles that show good biocompatibility, fast reductive degradation, and triggered intracellular drug release behavior.

Thermo and pH dual-controlled charge reversal amphiphilic graft copolymer micelles for overcoming drug resistance in cancer cells

A novel thermo and pH dual-controlled charge reversal PSMA₈₉-g-P(DMA₁₆-co-SD₅₆) graft copolymer micelle was developed with effectively enhanced cellular uptake for overcoming multi-drug resistance in cancer cells.

Reductively degradable α-amino acid-based poly(ester amide)-graft-galactose copolymers: facile synthesis, self-assembly, and hepatoma-targeting doxorubicin delivery

Multifunctional nanoparticles mediate specific and efficient intracellular doxorubicin delivery to asialoglycoprotein receptor-overexpressing hepatoma cells.

Reduction-triggered release of paclitaxel from in situ formed biodegradable core-cross-linked micelles

We provide a facile strategy to prepare redox-responsive core-crosslinked micelles for the controlled release of paclitaxel.

Nanomedicine in cancer therapy: challenges, opportunities, and clinical applications

Cancer is a leading cause of death worldwide. Currently available therapies are inadequate and spur demand for improved technologies. Rapid growth in nanotechnology towards the development of nanomedicine products holds great promise to improve therapeutic strategies against cancer. Nanomedicine products represent an opportunity to achieve sophisticated targeting strategies and multi-functionality. They can improve the pharmacokinetic and pharmacodynamic profiles of conventional therapeutics and may thus optimize the efficacy of existing anti-cancer compounds. In this review, we discuss state-of-the-art nanoparticles and targeted systems that have been investigated in clinical studies. We emphasize the challenges faced in using nanomedicine products and translating them from a preclinical level to the clinical setting. Additionally, we cover aspects of nanocarrier engineering that may open up new opportunities for nanomedicine products in the clinic.

Multifunctional Rbx WO3 nanorods for simultaneous combined chemo-photothermal therapy and photoacoustic/CT imaging

Light-triggered drug delivery based on near-infrared (NIR)-mediated photothermal nanocarriers has received tremendous attention for the construction of cooperative therapeutic systems in nanomedicine. Herein, a new paradigm of light-responsive drug carrier that doubles as a photothermal agent is reported based on the NIR light-absorber, Rb(x) WO3 (rubidium tungsten bronze, Rb-TB) nanorods. With doxorubicin (DOX) payload, the DOX-loaded Rb-TB composite (Rb-TB-DOX) simultaneously provides a burst-like drug release and intense heating effect upon 808-nm NIR light exposure. MTT assays show the photothermally enhanced antitumor activity of Rb-TB-DOX to the MCF-7 cancer cells. Most remarkably, Rb-TB-DOX combined with NIR irradiation also shows dramatically enhanced chemotherapeutic effect to DOX-resistant MCF-7 cells compared with free DOX, demonstrating the enhanced efficacy of combinational chemo-photothermal therapy for potentially overcoming drug resistance in cancer chemotherapy. Furthermore, in vivo study of combined chemo-photothermal therapy is also conducted and realized on pancreatic (Pance-1) tumor-bearing nude mice. Apart from its promise for cancer therapy, the as-prepared Rb-TB can also be employed as a new dual-modal contrast agent for photoacoustic tomography and (PAT) X-ray computed tomography (CT) imaging because of its high NIR optical absorption capability and strong X-ray attenuation ability, respectively. The results presented in the current study suggest promise of the multifunctional Rb(x)WO3 nanorods for applications in cancer theranostics.

Magnetic nanoparticle-based therapeutic agents for thermo-chemotherapy treatment of cancer

Magnetic nanoparticles have been widely investigated for their great potential as mediators of heat for localised hyperthermia therapy. Nanocarriers have also attracted increasing attention due to the possibility of delivering drugs at specific locations, therefore limiting systematic effects. The enhancement of the anti-cancer effect of chemotherapy with application of concurrent hyperthermia was noticed more than thirty years ago. However, combining magnetic nanoparticles with molecules of drugs in the same nanoformulation has only recently emerged as a promising tool for the application of hyperthermia with combined chemotherapy in the treatment of cancer. The main feature of this review is to present the recent advances in the development of multifunctional therapeutic nanosystems incorporating both magnetic nanoparticles and drugs, and their superior efficacy in treating cancer compared to either hyperthermia or chemotherapy as standalone therapies. The principle of magnetic fluid hyperthermia is also presented.

Polypeptide-based "smart" micelles for dual-drug delivery: a combination study of experiments and simulations

A dual-drug-loaded micelle is designed and constructed from a mixture of poly(propylene oxide)-b-poly(γ-benzyl-l-glutamate)-b-poly(ethylene glycol) (PPO-b-PBLG-b-PEG) triblock terpolymers and two model drugs, doxorubicin (DOX) and naproxen (Nap). In the micelles, the DOX is chemically linked to the PBLG backbones through an acid-cleavable hydrazone bond, whereas the Nap is physically encapsulated in the cores. The drug loading and releasing behaviors of the dual-drug-loaded micelles as well as single drug-loaded micelles (DOX-conjugated or Nap-loaded micelles) are studied. The structures of micelles are characterized by means of microscopies and dynamic light scattering, and further examined by dissipative particle dynamics (DPD) simulations. It is revealed that the micelles possess a core-shell-corona structure in which the PPO/Nap, PBLG/DOX, and PEG aggregate to form the core, shell, and corona, respectively. In vitro studies reveal that the release of DOX and Nap is pH- and thermosensitive. Such drug releasing behaviors are also examined by DPD simulations, and more information regarding the mechanism is obtained. In addition, the bio-related properties such as cellular uptake of the micelles and biocompatibility of the deliveries are evaluated. The results show that the dual-drug-loaded micelles are biocompatible at normal physiological conditions and retain the anti-cancer efficiency.

Reduction-responsive polymeric micelles and vesicles for triggered intracellular drug release

SIGNIFICANCE

The therapeutic effects of current micellar and vesicular drug formulations are restricted by slow and inefficient drug release at the pathological site. The development of smart polymeric nanocarriers that release drugs upon arriving at the target site has received a tremendous amount of attention for cancer therapy.

RECENT ADVANCES

Taking advantage of a high reducing potential in the tumor tissues and in particular inside the tumor cells, various reduction-sensitive polymeric micelles and vesicles have been designed and explored for triggered anticancer drug release. These reduction-responsive nanosystems have demonstrated several unique features, such as good stability under physiological conditions, fast response to intracellular reducing environment, triggering drug release right in the cytosol and cell nucleus, and significantly improved antitumor activity, compared to traditional reduction-insensitive counterparts.

CRITICAL ISSUES

Although reduction-sensitive micelles and polymersomes have accomplished rapid intracellular drug release and enhanced in vitro antitumor effect, their fate inside the cells including the mechanism, site, and rate of reduction reaction remains unclear. Moreover, the systemic fate and performance of reduction-sensitive polymeric drug formulations have to be investigated.

FUTURE DIRECTIONS

Biophysical studies should be carried out to gain insight into the degradation and drug release behaviors of reduction-responsive nanocarriers inside the tumor cells. Furthermore, novel ligand-decorated reduction-sensitive nanoparticulate drug formulations should be designed and explored for targeted cancer therapy in vivo.

Stimuli-Responsive Materials for Controlled Release of Theranostic Agents

Stimuli-responsive materials are so named because they can alter their physicochemical properties and/or structural conformations in response to specific stimuli. The stimuli can be internal, such as physiological or pathological variations in the target cells/tissues, or external, such as optical and ultrasound radiations. In recent years, these materials have gained increasing interest in biomedical applications due to their potential for spatially and temporally controlled release of theranostic agents in response to the specific stimuli. This article highlights several recent advances in the development of such materials, with a focus on their molecular designs and formulations. The future of stimuli-responsive materials will also be explored, including combination with molecular imaging probes and targeting moieties, which could enable simultaneous diagnosis and treatment of a specific disease, as well as multi-functionality and responsiveness to multiple stimuli, all important in overcoming intrinsic biological barriers and increasing clinical viability.

Targeted delivery of doxorubicin-loaded poly (ε-caprolactone)-b-poly (N-vinylpyrrolidone) micelles enhances antitumor effect in lymphoma

Background

The present study was motivated by the need to design a safe nano-carrier for the delivery of doxorubicin which could be tolerant to normal cells. PCL₆₃-b-PNVP₉₀ was loaded with doxorubicin (6 mg/ml), and with 49.8% drug loading efficiency; it offers a unique platform providing selective immune responses against lymphoma.

Methods

In this study, we have used micelles of amphiphilic PCL₆₃-b-PNVP₉₀ block copolymer as nano-carrier for controlled release of doxorubicin (DOX). DOX is physically entrapped and stabilized in the hydrophobic cores of the micelles and biological roles of these micelles were evaluated in lymphoma.

Results

DOX loaded PCL₆₃-b-PNVP₉₀ block copolymer micelles (DOX-PCL₆₃-b-PNVP₉₀) shows enhanced growth inhibition and cytotoxicity against human (K-562, JE6.1 and Raji) and mice lymphoma cells (Dalton's lymphoma, DL). DOX-PCL₆₃-b-PNVP₉₀ demonstrates higher levels of tumoricidal effect against DOX-resistant tumor cells compared to free DOX. DOX-PCL₆₃-b-PNVP₉₀ demonstrated effective drug loading and a pH-responsive drug release character besides exhibiting sustained drug release performance in in-vitro and intracellular drug release experiments.

Conclusion

Unlike free DOX, DOX-PCL₆₃-b-PNVP₉₀ does not show cytotoxicity against normal cells. DOX-PCL₆₃-b-PNVP₉₀ prolonged the survival of tumor (DL) bearing mice by enhancing the apoptosis of the tumor cells in targeted organs like liver and spleen.

Glyco-nanoparticles with sheddable saccharide shells: a unique and potent platform for hepatoma-targeting delivery of anticancer drugs

Reduction-sensitive shell-sheddable glyco-nanoparticles were designed and developed based on poly(ε-caprolactone)-graft-SS-lactobionic acid (PCL-g-SS-LBA) copolymer for efficient hepatoma-targeting delivery of doxorubicin (DOX). PCL-g-SS-LBA was prepared by ring-opening copolymerization of ε-caprolactone and pyridyl disulfide carbonate followed by postpolymerization modification with thiolated lactobionic acid (LBA-SH) via thiol-disulfide exchange reaction. The dynamic light scattering (DLS) and transmission electron microscopy (TEM) showed that PCL-g-SS-LBA was self-assembled into monodisperse nanoparticles (SS-GNs) with a mean diameter of about 80 nm. SS-GNs while remaining stable under physiological conditions (37 °C, pH 7.4) were prone to rapid shell-shedding and aggregation in the presence of 10 mM dithiothreitol (DTT). DOX was loaded into SS-GNs with a decent loading content of 12.0 wt %. Notably, in vitro release studies revealed that about 80.3% DOX was released from DOX-loaded SS-GNs in 24 h under a reductive condition while low drug release (<21%) was observed for DOX-loaded PCL-g-LBA nanoparticles (reduction-insensitive control) under otherwise the same condition and for DOX-loaded SS-GNs under a nonreductive condition. The flow cytometry and confocal microscopy observations indicated that SS-GNs were efficiently taken up by asialoglycoprotein receptor (ASGP-R)-overexpressing HepG2 cells likely via a receptor-mediated endocytosis mechanism and DOX was released into the nuclei of cells following 4 h incubation. MTT assays showed that DOX-loaded SS-GNs exhibited a high antitumor activity toward HepG2 cells, which was comparable to free DOX and about 18-fold higher than their reduction-insensitive counterparts, while blank SS-GNs were nontoxic up to a tested concentration of 1.0 mg/mL. These shell-sheddable glyco-nanoparticles are promising for hepatoma-targeting chemotherapy.

Acid-triggered drug release from micelles based on amphiphilic oligo(ethylene glycol)–doxorubicin alternative copolymers

We prepared pH-sensitive amphiphilic oligo(ethylene glycol)–doxorubicin alternative conjugates for the controlled release of doxorubicin.

Biodegradable multiblock polyurethane micelles with tunable reduction-sensitivity for on-demand intracellular drug delivery

Biodegradable polyurethanes bearing varied amounts of disulfide linkages in the backbone can rapidly enter tumor cells and efficiently transport the encapsulated payloads into cytosol, resulting in controlled inhibition effects against cancer cells. The nanocarriers are promising candidates for on-demand intracellular drug delivery applications.

Fibril-shaped aggregates of doxorubicin with poly-l-lysine and its derivative

Doxorubicin forms fibril-like aggregates in phosphate buffer and complexes with poly-l-lysine and cholate-grafted poly-l-lysine.

Reduction-cleavable polymeric vesicles with efficient glutathione-mediated drug release behavior for reversing drug resistance

In the treatment of cancer, multidrug resistance (MDR) has been the major obstacle to the success of chemotherapy. The underlying mechanism relies on the overexpression of drug-efflux transporters that prevent the intracellular transport of the drug. In this study, reduction-cleavable vesicles were designed and developed with efficient glutathione-mediated drug-release behavior for reversing drug resistance. Polymeric vesicles were self-assembled from triblock copolymers with disulfide-bond-linked poly(ethylene glycol) (PEG) and poly(ε-benzyloxycarbonyl-L-lysine) (PzLL). Observations from transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) outline an obvious hollow structure surrounded by a thin outer layer, indicating the successful formation of the vesicles. Using fluorescently detectable doxorubicin hydrochloride (DOX·HCl) as the model drug, a significant acceleration of drug release regulated by glutathione (GSH) was found (>3-fold difference). Upon incubation of the DOX·HCl-loaded polymeric vesicles with the HeLa cervical cancer cell line exposed to glutathione, an enhanced nuclear accumulation of DOX·HCl was observed, elicited by the preferred disassembly of the vesicle structure under reducing conditions. Importantly, by using the gemcitabine hydrochloride (GC·HCl)-resistant breast cancer cell line MDA-MB-231, it was found that cell viability was significantly reduced after treatment with GC·HCl-loaded polymeric vesicles, indicating that these vesicles can help to reverse the drug resistance.

Reversal of multidrug resistance by stimuli-responsive drug delivery systems for therapy of tumor

Multidrug resistance (MDR) is a major obstacle to successful cancer therapy, especially for chemotherapy. The new drug delivery system (DDS) provides promising approaches to reverse MDR, for which the poor cellular uptake and insufficient intracellular drug release remain rate-limiting steps for reaching the drug concentration level within the therapeutic window. Stimulus-coupled drug delivery can control the drug-releasing pattern temporally and spatially, and improve the accumulation of chemotherapeutic agents at targeting sites. In this review, the applications of DDS which is responsive to different types of stimuli in MDR cancer therapy is introduced, and the design, construction, stimuli-sensitivity and the effect to reverse MDR of the stimuli-responsive DDS are discussed.

Stimuli-responsive nanocarriers for drug delivery

Spurred by recent progress in materials chemistry and drug delivery, stimuli-responsive devices that deliver a drug in spatial-, temporal- and dosage-controlled fashions have become possible. Implementation of such devices requires the use of biocompatible materials that are susceptible to a specific physical incitement or that, in response to a specific stimulus, undergo a protonation, a hydrolytic cleavage or a (supra)molecular conformational change. In this Review, we discuss recent advances in the design of nanoscale stimuli-responsive systems that are able to control drug biodistribution in response to specific stimuli, either exogenous (variations in temperature, magnetic field, ultrasound intensity, light or electric pulses) or endogenous (changes in pH, enzyme concentration or redox gradients).

Targeted delivery of a phosphopeptide prodrug inhibits the proliferation of a human glioma cell line

Peptides are ideal candidates for developing therapeutics. Polo-like kinase 1 is an important regulatory protein in the cell cycle and contains a C-terminal polo-box domain, which is the hallmark of this protein family. We developed a peptide inhibitor of polo-like kinase 1 that targets its polo-box domain. This new phosphopeptide, cRGDyK-S-S-CPLHSpT, preferentially penetrates the cancer cell membrane mediated by the integrin receptor, which is expressed at high levels by cancer cells. In the present study, using high performance liquid chromatography and mass spectroscopy, we determined the stability of cRGDyK-S-S-CPLHSpT and its cleavage by glutathione under typical conditions for cell culture. We further assessed the ability of the peptide to inhibit the proliferation of the U87MG glioma cell line. The phosphorylated peptide was stable, and the disulfide bond of cRGDyK-S-S-CPLHSpT was cleaved in 50 mM glutathione. This peptide inhibited the growth of cancer cells and changed their morphology. Therefore, we conclude that the phosphopeptide shows promise as a prodrug and has a high potential to act as an anticancer agent by inhibiting polo-like kinase 1 by binding its polo-box domain. These findings indicate the therapeutic potential of PLHSpT and peptides similarly targeted to surface receptors of cancer cells and to the functional domains of regulatory proteins.

Redox-responsive alginate nanogels with enhanced anticancer cytotoxicity

Although doxorubicin (Dox) has been widely used in the treatment of different types of cancer, its insufficient cellular uptake and intracellular release is still a limitation. Herein, we report an easy process for the preparation of redox-sensitive nanogels that were shown to be highly efficient in the intracellular delivery of Dox. The nanogels (AG/Cys) were obtained through in situ cross-linking of alginate (AG) using cystamine (Cys) as a cross-linker via a miniemulsion method. Dox was loaded into the AG/Cys nanogels by simply mixing it in aqueous solution with the nanogels, that is, by the establishment of electrostatic interactions between the anionic AG and the cationic Dox. The results demonstrated that the AG/Cys nanogels are cytocompatible, have a high drug encapsulation efficiency (95.2 ± 4.7%), show an in vitro accelerated release of Dox in conditions that mimic the intracellular reductive conditions, and can quickly be taken up by CAL-72 cells (an osteosarcoma cell line), resulting in higher Dox intracellular accumulation and a remarkable cell death extension when compared with free Dox. The developed nanogels can be used as a tool to overcome the problem of Dox resistance in anticancer treatments and possibly be used for the delivery of other cationic drugs in applications beyond cancer.

FRET imaging reveals different cellular entry routes of self-assembled and disulfide bonded polymeric micelles

Although nanocarriers hold promise for cancer chemotherapy, their intracellular drug delivery pathways are not fully understood. In particular, the influence of nanocarrier stability on cellular uptake is still uncertain. By physically loading hydrophobic FRET probes, we revealed different intracellular drug delivery routes of self-assembled and disulfide bonded micelles. The self-assembled micelles were structurally dissociated by micelle-membrane interactions, and the hydrophobic probes were distributed on the plasma membrane. Alternatively, intact disulfide bonded micelles carrying hydrophobic probes were internalized into cancer cells via multiple endocytic pathways. Following internalization, disulfide bonded micelles were decomposed in early endosomes by glutathione-mediated disulfide bond reduction, exposing the probes to intracellular organelles.

Self-assembled graphene-dextran nanohybrid for killing drug-resistant cancer cells

A nanohybrid based on nanoscale graphene oxide (NGO) and dextran has been designed and employed for effectively killing drug-resistant MCF-7/ADR cells. This graphene-based nanohybrid was readily prepared through π-π interaction of NGO and hematin-terminated dextran (HDex), being denoted as NGO-HDex. It revealed an improved stability in physiological conditions as compared to native NGO. Besides, NGO-HDex could efficiently load doxorubicin (DOX), an anticancer drug, with drug loading capacity of 3.4 mg/mg NGO and liberate the drug with a pH-dependent profile. Cell viability assay indicated that the NGO-HDex displayed lower cytotoxicity against MCF-7/ADR cells as compared to native NGO. DOX-loaded NGO-HDex, however, revealed more efficient killing effect in the cells than free DOX because the nanohybrid caused a higher amount of DOX accumulated in the cells. The results of this study highlight that the NGO-HDex has high potential for killing drug-resistant cancer cells.

Tumor extracellular acidity-activated nanoparticles as drug delivery systems for enhanced cancer therapy

pH-responsive nanoparticles (NPs) are currently under intense development as drug delivery systems for cancer therapy. Among various pH-responsiveness, NPs that are designed to target slightly acidic extracellular pH environment (pHe) of solid tumors provide a new paradigm of tumor targeted drug delivery. Compared to conventional specific surface targeting approaches, the pHe-targeting strategy is considered to be more general due to the common occurrence of acidic microenvironment in solid tumors. This review mainly focuses on the design and applications of pHe-activated NPs, with special emphasis on pHe-activated surface charge reversal NPs, for drug and siRNA delivery to tumors. The novel development of NPs described here offers great potential for achieving better therapeutic effects in cancer treatment.

Reduction-sensitive Nanosystems for Active Intracellular Drug Delivery

The past several years have witnessed explosive progress in reduction-sensitive nanosystems that are stable under physiological conditions, but rapidly destabilized under a reducing environment for “active” intra-cellular drug delivery. The uniqueness of the disulfide chemistry has enabled versatile design of smart nanosystems ranging from reduction-sensitive degradable micelles, polymersomes, nanogels and capsules to nanoparticles. This superior intra-cellular drug release approach has been shown to significantly enhance drug efficacy, overcome multi-drug resistance (MDR) and/or reduce drug- and carrier-associated side effects. In vivo studies have demonstrated that reduction-sensitive reversibly cross-linked nanosystems result in enhanced stability, longer circulation time, improved tumor-targetability and better therapeutic outcomes as compared to the non-cross-linked controls as well as to free drugs. It is anticipated that reduction-sensitive nanosystems will play a relevant role in the arena of targeted cancer therapy.

Versatile fluorescence resonance energy transfer-based mesoporous silica nanoparticles for real-time monitoring of drug release

We describe the development of a versatile fluorescence resonance energy transfer (FRET)-based real-time monitoring system, consisting of (a) coumarin-labeled-cysteine tethered mesoporous silica nanoparticles (MSNs) as the drug carrier, (b) a fluorescein isothiocyanate-β-cyclodextrin (FITC-β-CD) as redox-responsive molecular valve blocking the pores, and (c) a FRET donor-acceptor pair of coumarin and FITC integrated within the pore-unlocking event, thereby allowing for monitoring the release of drugs from the pores in real-time. Under nonreducing conditions, when the disulfide bond is intact, the close proximity between coumarin and FITC on the surface of MSNs results in FRET from coumarin to FITC. However, in the presence of the redox stimuli like glutathione (GSH), the disulfide bond is cleaved which leads to the removal of molecular valve (FITC-β-CD), thus triggering drug release and eliminating FRET. By engineering such a FRET-active donor-acceptor structure within the redox-responsive molecular valve, we can monitor the release of the drugs entrapped within the pores of the MSN nanocarrier, following the change in the FRET signal. We have demonstrated that, any exogenous or endogenous change in the GSH concentration will result in a change in the extent of drug release as well as a concurrent change in the FRET signal, allowing us to extend the applications of our FRET-based MSNs for monitoring the release of any type of drug molecule in real-time.

Stimulus-sensitive polymeric nanoparticles and their applications as drug and gene carriers

Polymeric nanoparticles are promising candidates as drug and gene carriers. Among polymeric nanoparticles, those that are responsive to internal or external stimuli are of greater interest because they allow more efficient delivery of therapeutics to pathological regions. Stimulus-sensitive polymeric nanoparticles have been fabricated based on numerous nanostructures, including micelles, vesicles, crosslinked nanoparticles, and hybrid nanoparticles. The changes in chemical or physical properties of polymeric nanoparticles that occur in response to single, dual, or multiple stimuli endow these nanoparticles with the ability to retain cargoes during circulation, target the pathological region, and release their cargoes after cell internalization. This Review focuses on the most recent developments in the preparation of stimulus-sensitive polymeric nanoparticles and their applications in drug and gene delivery.

Redox and pH-responsive degradable micelles for dually activated intracellular anticancer drug release

Redox and pH dual-responsive biodegradable micelles were developed based on poly(ethylene glycol)-SS-poly(2,4,6-trimethoxybenzylidene-pentaerythritol carbonate) (PEG-SS-PTMBPEC) copolymer and investigated for intracellular doxorubicin (DOX) release. PEG-SS-PTMBPEC copolymer with an Mn of 5.0-4.1kg/mol formed micellar particles with an average diameter of 140nm and a low polydispersity of 0.12. DOX was loaded into PEG-SS-PTMBPEC micelles with a decent drug loading content of 11.3wt.%. The in vitro release studies showed that under physiological conditions only ca. 24.5% DOX was released from DOX-loaded micelles in 21h. The release of DOX was significantly accelerated at pH5.0 or in the presence of 10mM glutathione (GSH) at pH7.4, in which 62.8% and 74.3% of DOX was released, respectively, in 21h. The drug release was further boosted under 10mM GSH and pH 5.0 conditions, with 94.2% of DOX released in 10h. Notably, DOX release was also facilitated by 2 or 4h incubation at pH 5.0 and then at pH 7.4 with 10mM GSH, which mimics the intracellular pathways of endocytosed micellar drugs. Confocal microscopy observation indicated that DOX was delivered and released into the nuclei of HeLa cells following 8h incubation with DOX-loaded PEG-SS-PTMBPEC micelles, while DOX was mainly located in the cytoplasm for reduction-insensitive PEG-PTMBPEC controls. MTT assays revealed that DOX-loaded PEG-SS-PTMBPEC micelles had higher anti-tumor activity than reduction-insensitive controls, with low IC50 of 0.75 and 0.60μg/mL for HeLa and RAW 264.7 cells, respectively, following 48h incubation. PEG-SS-PTMBPEC micelles displayed low cytotoxicity up to a concentration of 1.0mg/mL. These redox and pH dual-bioresponsive degradable micelles have appeared as a promising platform for targeted intracellular anticancer drug release.

Synergistic targeting of cancer and associated angiogenesis using triple-targeted dual-drug silica nanoformulations for theragnostics

The targeting and therapeutic efficacy of dye- and dual-drug-loaded silica nanoparticles, functionalized with triple targeting ligands specific towards cancer and neoangiogenesis simultaneously, are discussed. This synergized, high-precision, multitarget concept culminates in an elevated uptake of nanoparticles by cancer and angiogenic cells with amplified proficiency, thereby imparting superior therapeutic efficacy against breast cancer cells and completely disabling the migration and angiogenic sprouting ability of activated endothelial cells. The exceptional multimodal efficiency achieved by this single therapeutic nanoformulation holds promise for the synergistic targeting and treatment of the yet elusive cancer and its related angiogenesis in a single, lethal shot.